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G4+ BMW Plugin - Post Start reving to 2k RPM??


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Hi, I'm hoping to get some help with a post start high-rpm condition.

When cold the engine cranks and fires ok but immediately jumps to 2k RPM and sits there for about 2 seconds then starts backing off slowly down to about 1k RPM. I've tried mucking with the fuel table for post-start enrichment, post start hold time and post start decay time with little impact on the initial 2k RPM as soon as it start. All I succeed in doing is making it harder to start and then harder to keep running once it starts without konking out. I've set the Crank Enrichment and Post Start Enrichment values back to the BMW E36 G4+ Extreme Plugin defaults as this is where it starts and does the post-start the best.

Surely reving to 2k RPM as soon as it starts isn't required though and 1200-1500 RPM would be plenty - but, how to adjust it.

The hot tune is very good (done by Graham at WRC Developments Napier) but the cold tune isn't so good - Graham didn't have time to do this. I've managed to get the Warm Up Enrichment working great + Accel Cold Correction going well by slowly adjusting the values each day until it drives nicely. It's now good from cold through to running temp. It's only the initial post start 2k RPM I can't figure out.

Any ideas?

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Good day.

It sounds like your idle speed control valve might be regulating itself causing more by pass air to enter the engine than necessary for idle causing the engine speed to raise momentarily as you have described. It's unlikely that incorrect fuel or ignition advance can cause the described, however, I stand to be corrected. What you can do when the engine starts up, or even before the engine starts up for that matter, open up the PCLink software and connect to your Link ECU. When connected press F12 to open up the run time values then navigate to the auxiliary tab. Proceed to start the engine while paying attention to the Idle Speed section of the windows in the lower left had corner. You should see the duty cycle reflected as a percentage change in relation to the engine speed. If such is the case then you can open up ECU Settings (View on the main menu of PCLink then select ECU Settings), navigate and open up the Idle Speed Control entry and within Idle Speed Control you should turn your attention to the Startup Step Table as well as the Idle Base Position Table for adjustments to correct the described problem. You may choose to view these tables live during startup or you may choose to enable PC Logging to capture the data for you to be reviewed while the engine is off. Don't forget to press the F1 key while you are on the respective tables to get detailed help file information relative to tasks you may be undertaking.


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Damien, you were spot-on. It was the Idle Base Position Table values causing it. I adjusted the default value of 45% down to 35% and the post-start idle speed now goes to 1500RPM.

I'll tweak it a little more over the coming days to see if I can get it down to 1200-1300RPM and still have the car start well. This was one place I didn't think to check - thanks again for your help.

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